Tteok is a class of Korean rice cakes made with glutinous rice flour (also known as sweet rice or chapssal in Korean), by steaming. Normal rice flour can also be used for some kinds of tteok and there are hundreds of different kinds of tteok eaten year round. In Korea, it is customary to eat tteokguk on New Year's Day and sweet tteok at weddings and/or on birthdays. It is often considered a celebratory food and can range from rather elaborate versions with nuts and fruits down to the plain-flavored tteok used in home cooking. Some common ingredients for many kinds of tteok are mung bean, red bean, and sweet red bean paste. It can also include variations of dried fruits, sesame seeds, oil, and sugar.